html body {
    height: 100%;
    width: 100%;
    margin: 0;
    padding: 0;
    overflow: hidden;
  }


  .float_layout {
    position: absolute;
    top: 0;
    background-color: white;
    z-index: 20;
  }

  .btn {
    width: 150px;
    height: 50px;
    color: white;
    margin-top: 10px;
    border-radius: 20px;
    margin-left: 10px;
  }


#left_cover{
    position: absolute;
  top: 0;
  width: 200px;
  height: 100%;
  left: 0;
  background-color: transparent;
  z-index: 0;
  /* background-color: red; */

  background-image: linear-gradient(
      to left,
      rgba(0,0,0,0) 0%,
      rgba(0,0,0,0.4) 60%,
      rgba(0,0,0,0.6) 80%,
      rgba(0,0,0,1) 100%);
}
#top_cover{
    position: absolute;
  top: 0;
  width: 100%;
  height: 80px;
  left: 0;
  background-color: transparent;
  z-index: 1;

  /* 表示从下往上百分比排列颜色 */
  background-image: linear-gradient(
      to top, 
      rgba(0,0,0,0.0) 10%,
      rgba(0,0,0,0.2) 20%,
      rgba(0,0,0,0.6) 50%,
      rgba(0,0,0,1) 100%);


   display: flex;
   flex-direction: row ;
   justify-content: center;
   align-items: center;
}

#right_cover{
    position: absolute;
  top: 0;
  width: 200px;
  height: 100%;
  right: 0;
  background-color: transparent;
  z-index: 0;

  background-image: linear-gradient(
      to right,
      rgba(0,0,0,0) 0%,
      rgba(0,0,0,0.4) 60%,
      rgba(0,0,0,0.6) 80%,
      rgba(0,0,0,1) 100%);
}

.ic_menu{
    margin-left: 50px;
    margin-top: 100px;
}

.ic_item{
    width: 50px;height: 50px;
    margin-top: 40px;
}

.txt_item{
  color: white;
  font-size: 12px;
  margin-top: 5px;
  align-items: center;
}